Coalition efforts to present a united front over the riots have come under strain as senior Liberal Democrats call for an end to "kneejerk" reactions by politicians and warn that stripping those involved of their benefits could worsen crime on the streets.

In a clear sign of tensions between the governing parties, the Lib Dems' deputy leader, Simon Hughes, insists that long-term solutions lie in supporting communities by offering opportunities and redistributing wealth, not slashing help from the state and cutting taxes for the rich.

Writing in the Observer, he says: "We need to demonstrate ambition to have a responsible society where all people understand and are aware of their obligations to each other. This means we must not cut taxes for the rich or take away public support for the needy."

Referring to plans, backed by many Tories, to cut benefits and evict families of rioters and looters from their homes, Hughes, whose south London constituency of Bermondsey and Old Southwark has one of the highest concentrations of council homes, adds: "We should be careful not to rush into kneejerk solutions including over-hasty moves to change the social contract and approaches to sentences which may have the reverse effect to that intended."

As Lib Dem leader Nick Clegg also cautioned against "kneejerk" reactions, Hughes's comments were backed by the Lib Dems' welfare spokeswoman, Jenny Willott, who said she was "very worried" about moves to cut benefits for those involved in the riots, when the same punishment would not apply to others who had committed equally serious offences.

"One obvious problem would be that if people don't have money they would turn more to acquisitive crime. I completely understand people's desire to stamp out the problem, but it is important that we do not make things worse," Willott said.

With the support of David Cameron, Conservative Wandsworth council was the first to attempt to evict tenants who had been caught up in the rioting. The prime minister also pledged to support "zero tolerance" policing where minor offences are prosecuted and said a series of tough measures would be unveiled in coming months to fight crime and reclaim the streets. "We haven't talked the language of zero tolerance enough but the message is getting through," he said.

Wandsworth announced on Friday that the first eviction notice had been served – to the mother of an 18-year-old boy accused of violent disorder and attempted theft. The teenager has not yet been convicted but has appeared in court in connection with disturbances on Monday at Clapham Junction.

Other authorities, including Westminster, Greenwich, Hammersmith and Fulham, Nottingham and Salford, are also considering evicting those found to have taken part in the unrest.

An eviction notice is the first step leading to a final decision made by a judge sitting in a county court.

Chris Goulden, programme manager at the Joseph Rowntree Foundation charity, condemned the actions. "There's a real danger here. The courts are there to punish wrongdoing through the justice system. It's not fair for a family to suffer because of the action of one individual. It means families who happen to be living in that kind of accommodation are punished twice, double what anyone else in society would be."

Kate Green, Labour MP and former chief executive of Child Poverty Action Group, said the evictions were wrong. "It's absolutely right that people should go through the due process of the courts but these evictions are something entirely different. That a whole family should be evicted because of the behaviour of one family member, and their siblings should be made homeless, is not right at all.

"Children in effect are being penalised twice for the socially excluded situation in which they are being brought up in a way that children from other families would never be."

Hughes also argues that while tough sentences should be handed down to previous offenders and those "who should set the best examples", such as parents and people in work, the system should treat young people with no criminal records with care. "We must be careful with punishments for young people with no previous criminal record; for some of those of school age or out of school with no work and no prospects, short custodial sentences could be no deterrent at all. A community which has so far offered them little may equally treat its judgments with little respect."

In an interview with the Observer, Ed Miliband says that unless Cameron announces a full public inquiry within 48 hours, he will set up Labour's own inquiry to examine the causes of the riots in a "national conversation" with people in rundown areas and those that have recovered from deprivation. "It's simply not good enough to go in for old-fashioned thinking, saying these are problems confined to an underclass," he said.

"Decisions should not be rushed. And it is about some young people who feel they have no stake in society when they see Britain's parallel worlds with huge gaps between rich and poor. That is why we need a national conversation. The prime minister seems afraid of a commission of inquiry. He seems afraid of the complex truth."

Speaking during a visit to riot-hit businesses in Liverpool and Manchester, the deputy prime minister said the government would commission independent research into the collapse of public order. Clegg also defended the right of local authorities to consider evicting the families of vandals and looters but stressed that the issue had to be dealt with carefully and sensitively.

• A man and a teenager have been charged with the murder of three men who were hit by a car while protecting shops in Birmingham. Joshua Donald, 26, from Ladywood, in the city, and a 17-year-old youth from Winson Green were charged with the murders of Haroon Jahan, 21, and brothers Shahzad Ali, 30, and Abdul Musavir, 31. All three were pronounced dead in hospital after being struck by a car last week.